Interpretive Summary: Fruit flies include some of the most important pests of fruits and vegetables, causing billions of dollars in losses worldwide. The majority of the pest species are exotic to the U.S., but their introduction threatens U.S. agriculture. They also severely limit the international markets for the fruit products of many U.S. trading parnters. To prevent the introduction of the Mexican fruit fly, the papaya fruit fly, the apple maggot, and other pest species, taxonomic tools are needed to identify them and related flies that might be mistaken for them. This paper provides such tools (keys, illustrations, descriptions) for three genera closely related to the aforementioned pests. It will be useful to APHIS-PPQ and other regulatory agencies responsible for quarantines to prevent the spread of pest fruit flies and for detecting new pest introductions into the U.S.